Patent Literature 1 discloses that, in a gate power supply device that supplies a gate power supply to a gate driving circuit for applying a gate voltage to a semiconductor device, a gate power self-supply circuit receives an off-time voltage of the semiconductor device, resistance-divides the voltage, and charges the voltage in a capacitor to self-supply the gate power supply and, when the off-time voltage of the semiconductor device drops and the gate power self-supply circuit cannot accumulate charges enough for maintaining a gate voltage in the capacitor, a backup power supply circuit receives the voltage of the gate power self-supply circuit, resistance-divides the voltage, and charges the voltage in the capacitor of the gate power self-supply circuit via a diode. Consequently, according to Patent Literature 1, the gate voltage can be supplied to the gate driving circuit of the semiconductor device of itself from the backup power supply circuit even if an external power supply is not provided. Therefore, when a plurality of the semiconductor devices are connected in parallel, it is possible to secure the gate power supply even if one semiconductor device fails due to short circuit.
Patent Literature 2 discloses that, in an inverter device, a commercial power supply is connected to an inverter main body, a parameter unit is connected to the inverter main body via a parameter communication cable, and an external power supply unit is connected to the parameter unit. Consequently, according to Patent Literature 2, even in a state in which the commercial power supply cannot be input during the start of the inverter main body, it is possible to check and change setting values.